Electron Spin-relaxation Dynamics in GaAs/AlGaAs Quantum Wells and InGaAs/InP Quantum Wells

Abstract

We have investigated the spin-relaxation process of electrons at room temperature in undoped GaAs/AlGaAs multiple-quantum wells (MQWs) and InGaAs/InP MQWs. The spin-relaxation times are measured for different well thicknesses using time-resolved spin-dependent pump and probe absorption measurement. The spin-relaxation time, τ s , for GaAs MQWs was found to depend on the electron confinement energy, E 1e , according to τ s ∝ E 1e -2.2 , demonstrating that the main spin-relaxation mechanism at room temperature is the D'yakonov-Perel' process. The measured spin-relaxation times of InGaAs MQWs whose band-gap is about half that of GaAs MQWs are about 5 ps and vary depending on the quantum confinement energy, E 1e , according to τ s ∝ E 1e -1.0 . The spin-relaxation time by Elliott-Yafet process, which becomes stronger for narrower band-gap materials, is calculated for quantum wells and shown to vary according to τ s ∝ E 1e -1 . The spin-relaxation mechanism and possible applications using this fast spin-relaxation process are discussed.